This disclosure provides for a method for a laser ablation technique for electrical contact to a buried electrically conducting layer in diamond. Furthermore this disclosure provides for a device that has a single crystal diamond substrate with a buried electrically conducting layer between two openings formed by the laser ablation technique and having electrical contacts and wherein the resistance measured between the openings is dominated by the buried electrically conducting layer and on the order of about 1 kΩ.
This disclosure demonstrates a facile method to make low-resistance electrical contact to a buried conducting layer in diamond.
Previous methods for establishing contact to a buried, electrically conducting layer in an otherwise insulating diamond have not overcome the obstacles and have do not produced the superior results of the technique disclosed herein.
One example of a previous method is multiple ion implants into diamond (Prins, 1985). This method for establishing electrical contact to the buried implant layer involves performing a series of ion implants over a range of energies to create a damaged diamond region which extends from the surface to the implant layer. Depending on the depth of the buried layer, this method requires many ion implants. Performing many ion implants is a costly and time-consuming procedure requiring highly specialized equipment and skilled personnel to provide maintenance and operation. Furthermore, using the multiple implant method, the electrical contacts to the buried layer must be established before the buried layer is formed by ion implantation.
A second example of a previous method is a laser damage column (Prawer, 1992). This alternative method establishes electrical contact to the buried layer by creating a column of damaged, electrically conducting diamond which extends from the diamond surface to the buried layer using pulsed focused laser irradiation coupled to a conventional microscope with a 50× objective. If the buried layer is slightly opaque, the laser pulse is selectively absorbed in the buried layer. The laser melts the diamond and this melt front propagates to the surface. Upon cooling, highly conductive columns extend from the surface to the buried layer. A disadvantage of this method is that the columns of damaged, electrically conducting material create relatively large contact resistances to the buried layer.
A third example of a previous method is ion implant over gold beads (Olivero, 2009). This alternative is to scan an ion beam along a linear path which terminates at a semi-spherical mask characterized by a non-uniform thickness profile (Au bead made with ball bonder). As the beam scan progresses towards the center of the mask, incident ions cross an increasing thickness of masking material, thus progressively reducing their range in the diamond layer. After removing the mask, the heavily damaged, electrically conducting diamond can be connected with the surface and the implant layer establishing electrical contact. A disadvantage of this method is that irregularities in the semi-spherical mask create discontinuities in the electrically conducting column such that robust electrical contact between the diamond surface and the buried layer is not reliable.